BK virus associated hemorrhagic cystitis in pediatric patients undergoing hematopoietic stem cell transplantation

Abstract Background BK virus (BKV) is one of the most common causes of hemorrhagic cystitis (HC) in children undergoing hematopoietic stem cell transplantation (HSCT). Methods Descriptive and retrospective study that included patients from 0-18 years old undergoing HSCT with a diagnosis of HC, admitted from 1/1/2018 to 11/30/2023 in a tertiary care pediatric hospital. Patients with HC were tested for BKV by quantitative polymerase chain reaction (PCR) in urine samples, if positive, plasma viral load was also requested. BKV-HC grading was defined by the European Conference on Infections in Leukemia (ECIL) consensus document. Asymptomatic patients did not undergo standardized screening for BKV. Results During this period 86 HSCT were performed for either malignant (75,6%) or non-malignant disorders (24,4%). Overall, 16 (18,6%) were autologous and 70 (81.4%) were allogeneic: 40 human leukocyte antigen (HLA) matched unrelated donor, 26 HLA-matched related donor and 4 haploidentical. Six patients (7%) suffered HC, all associated with BKV as the cause. These six patients underwent allogeneic HSCT, and 4 of them had HLA-matched unrelated donors. All patients were over 5 years old. Male sex predominated (n:5). All of the patients had hematologic malignancies as the underlying diagnosis (5 with acute lymphoblastic leukemia - ALL). The stem cell source was bone marrow in 3 patients and peripheral blood in the other 3. All patients received myeloablative conditioning regimen and 4 underwent total body irradiation. Only one patient received post-transplant cyclophosphamide. Symptoms (dysuria, abdominal pain, macroscopic hematuria, clots) began more than 14 days after HSCT in 100% of the cases. Hematuria was categorized as grade III in 5 patients and grade IV (severe) only in one. All patients tested positive for BKV PCR in urine samples. High-level BK viruria (>107 copies/mL) was found in 66,6%. BK viremia was detected in 4 patients. All of the patients had another concomitant viral infection, with cytomegalovirus reactivation being the most frequent (n:4). Two patients also had detectable adenovirus (ADV) PCR in urine samples. Acute graft versus host disease (GVHD) was diagnosed in 5 patients, all with skin involvement. All patients were hospitalized and prolonged the length of stay. Regarding treatment, they all received hyperhydration and Cidofovir (more than 3 doses). Dose of immunosuppressive treatment was reduced in 5 cases. Acute kidney failure (AKF) was found in 3 patients. One patient developed chronic kidney failure. The patient with no GVHD was the one who improved the fastest. The patient with severe hematuria required bladder irrigation, had dialysis indication and presented a related death. Conclusion The development of BKV-HC in HSCT patients results in suffering and pain, prolonged hospitalizations and significant morbidity (AKF). Literature shows that male sex, older age and acute GVHD are important risk factors, and this is what we also found in our case series. BKV-HC is considered a difficult and severe condition to manage, remaining troublesome so we should overcome this deficiency with new approaches, particularly emphasizing in preemptive or prophylaxis measures for the benefit of our patients.